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Verifiable Credential

To combat greenwashing and provide high-assurance data, the draft recommends linking to a W3C Verifiable Credential (VC). This structure allows a trusted third party (like an environmental auditor) to cryptographically sign the metrics you have published at the .well-known/sustainability-data URI.

Here is an Example Draft structure for the Verifiable Credential, following the W3C VC Data Model and aligned with the metrics in draft-besleaga-sustainability-wellknown.

Draft Verifiable Credential (JSON-LD)

{
  "@context": [
    "https://www.w3.org/2018/credentials/v1",
    "https://w3id.org/security/suites/ed25519-2020/v1",
    {
      "SustainabilityReport": "https://example.org/vocab#SustainabilityReport",
      "energyConsumption": "https://example.org/vocab#energy-consumption",
      "carbonFootprint": "https://example.org/vocab#carbon-footprint",
      "reportingPeriod": "https://example.org/vocab#reporting-period",
      "provider": "https://example.org/vocab#provider"
    }
  ],
  "id": "urn:uuid:5842197a-9761-464a-95f0-802528a4787a",
  "type": ["VerifiableCredential", "SustainabilityReportCredential"],
  "issuer": "did:web:auditor.example.com",
  "issuanceDate": "2026-03-21T10:00:00Z",
  "credentialSubject": {
    "id": "did:web:example.com",
    "version": "2.0",
    "capabilities": "extended",
    "provider": "Example Corp",
    "reporting-period": "2025",
    "target": "example.com",
    "measurement-method": "hardware-metered",
    "methodology-uri": "https://example.com/sustainability/methodology",
    "energy-consumption": 13540.0,
    "energy-unit": "kWh",
    "carbon-footprint": 3720.5,
    "carbon-unit": "kgCO2e"
  },
  "proof": {
    "type": "Ed25519Signature2020",
    "created": "2026-03-21T10:05:00Z",
    "verificationMethod": "did:web:auditor.example.com#key-1",
    "proofPurpose": "assertionMethod",
    "proofValue": "z58D63V...[cryptographic-signature-hash]..."
  }
}

Key Components Explained

  • issuer: This is the Decentralized Identifier (DID) of the authoritative entity (e.g., a certified carbon auditor) that verified the data.
  • credentialSubject: This block mirrors fields defined in the draft — the mandatory members (such as reporting-period and the target reporting subject) plus reported metrics like energy-consumption and carbon-footprint. It serves as the "claims" being made.
  • proof: This is the cryptographic signature. It ensures that if even a single digit of the energy consumption is changed in the .well-known file, the VC signature will no longer match, alerting the client to a potential misrepresentation.

Anti-Greenwashing

By hosting this VC at the URL specified in your verifiable-attestation-uri field, you provide a "discovery surface" for automated tools to verify your sustainability claims against external authoritative reports.

Implementation Workflow

Generate Metrics: Run your internal sustainability reporting tools to generate the JSON for /.well-known/sustainability-data.

Audit

Provide the raw data and methodology to an auditor.

Issue VC

The auditor generates this VC and signs it with their private key.

Publish

You host the signed VC at a public URL and update the verifiable-attestation-uri field in your well-known metadata to point to it.